Adjusting blind decoding of downlink control channel

ABSTRACT

The present disclosure is related to adjusting a blind decoding of a downlink control channel in a base station. A method of adjusting a blind decoding of a downlink control channel may include creating an enhanced physical downlink control channel (EPDCCH) using the number of EPDCCH candidates per aggregation level (AL) in each of one or more EPDCCH sets for user equipment; and transmitting the created EPDCCH to the user equipment. Herein, the number of EPDCCH candidates is determined based on at least one of (i) a resource size associated with configuration of each EPDCCH set and (ii) the total number of EPDCCH sets.

TECHNICAL FIELD

The present disclosure relates to adjusting a blind decoding of adownlink control channel. Particularly, the present disclosure relatesto a method and an apparatus for adjusting a blind decoding of userequipment, in the case that the user equipment is configured to receivedownlink control information (DCI) through an enhanced physical downlinkcontrol channel (EPDCCH).

BACKGROUND ART

As communication systems make progress, consumers such as businessentities and individuals have used a large variety of wireless terminals(or devices). Mobile communication systems such as a long term evolution(LTE) or a LTE-Advanced (LTE-A) system associated with current 3GPPstandards may be a high-speed and large-capacity communication systemwhich is out of voice-centered service and can transmit/receive avariety of data including image, wireless data, and the like.Particularly, in the mobile communication system, a technology capableof a large-capacity data transmission equivalent to data transmission ina wired telecommunication network is desired.

Meanwhile, as information to be carried through a downlink controlchannel increases, a new EPDCCH has been introduced. However, the numberof blind decodings in an EPDCCH search space may not be controlled.Accordingly, in this case, there may be a problem that a blind decodingtime increases.

DISCLOSURE OF INVENTION Technical Problem

In order to overcome such problem, in the case that user equipment isconfigured to receive downlink control information (DCI) through anEPDCCH corresponding to a downlink control channel, the presentembodiment may provide a method and an apparatus for adjusting a blinddecoding of the user equipment. More specifically, the presentembodiment may provide a method and an apparatus for determining thenumber of blind decoding candidates in one or more EPDCCH sets (i.e.,EPDCCH monitoring sets), based on the number of EPDCCH sets and aresource size associated with configuration of each EPDCCH set.Furthermore, the present embodiment may provide a method and anapparatus for adjusting a blind decoding procedure of user equipmentusing the determined number of blind decoding candidates.

Technical Solution

In accordance with at least one embodiment, a method may be provided foradjusting transmission of a downlink control channel in a base station.The method may include creating an enhanced physical downlink controlchannel (EPDCCH) using the number of EPDCCH candidates per aggregationlevel (AL) in each of one or more EPDCCH sets for user equipment; andtransmitting the created EPDCCH to the user equipment. Herein, thenumber of EPDCCH candidates may be determined based on at least one of(i) a resource size associated with configuration of each EPDCCH set and(ii) the total number of EPDCCH sets.

In accordance with another embodiment, a method may be provided foradjusting a blind decoding of a downlink control channel in userequipment. The method may include receiving a downlink signal from abase station; and performing a blind decoding procedure in an EPDCCHregion of the received downlink signal, by applying the number of EPDCCHcandidates per aggregation level (AL) in each of one or more EPDCCHsets. Herein, the number of EPDCCH candidates may be determined based onat least one of (i) a resource size associated with configuration ofeach EPDCCH set and (ii) the total number of EPDCCH sets.

In accordance with still another embodiment, a base station may beprovided for adjusting transmission of a downlink control channel. Thebase station may include a control processor and a transmitter. Thecontrol processor may be configured to create an enhanced physicaldownlink control channel (EPDCCH) using the number of EPDCCH candidatesper aggregation level (AL) in each of one or more EPDCCH sets for userequipment. The transmitter may be configured to transmit the createdEPDCCH to the user equipment. Herein, the number of EPDCCH candidatesmay be determined based on at least one of (i) a resource sizeassociated with configuration of each EPDCCH set and (ii) the totalnumber of EPDCCH sets.

In accordance with still another embodiment, user equipment may beprovided for adjusting a blind decoding of a downlink control channel.The user equipment may include a receiver and a control processor. Thereceiver may be configured to receive a downlink signal from a basestation. The control processor may be configured to perform a blinddecoding in an EPDCCH region of the received downlink signal, byapplying the number of EPDCCH candidates per aggregation level (AL) ineach of one or more EPDCCH sets. Herein, the number of EPDCCH candidatesis determined based on at least one of (i) a resource size associatedwith configuration of each EPDCCH set and (ii) the total number ofEPDCCH sets.

Advantageous Effects

In the case that user equipment is configured to receive an EPDCCHcorresponding to a downlink control channel, the present embodiment mayenable the user equipment to perform a blind decoding procedure within‘the number of times determined based on an EPDCCH set characteristic’(e.g., the number of times determined in proportion to a size of anEPDCCH set), and thereby improving a blind decoding performance of theuser equipment in an EPDCCH search space. Herein, the size of an EPDCCHset corresponds to a characteristic of the EPDCCH set of the userequipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a structure for configuration of EPDCCH sets for acertain user equipment in accordance with at least one embodiment.

FIG. 2 illustrates the number of EPDCCH candidates in a case ofcombining Embodiment 1 and Formula 1 in accordance with at least oneembodiment.

FIG. 3 illustrates the number of EPDCCH candidates in a case ofcombining Embodiment 2 and Formula 3 in accordance with at least oneembodiment.

FIG. 4 illustrates a procedure of creating an EPDCCH based ondetermination of the number of blind decodings and transmitting thecreated EPDCCH, in a base station in accordance with at least oneembodiment.

FIG. 5 illustrates a procedure of adjusting a blind decoding procedurein an EPDCCH region using the number of blind decodings, in userequipment in accordance with at least one embodiment.

FIG. 6 is a diagram illustrating a structure of a base station inaccordance with some embodiments.

FIG. 7 is a diagram illustrating a structure of user equipment inaccordance with some embodiments.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription, the same elements will be designated by the same referencenumerals although they are shown in different drawings. Furthermore, inthe following description of the present embodiment, a detaileddescription of known functions and configurations incorporated hereinwill be omitted when it may make the subject matter of the presentembodiment unclear.

A wireless communication system in accordance with at least oneembodiment may be widely used in order to provide a variety ofcommunication services such as a voice service, a packet data service,and so forth. The wireless communication system may include userequipment (UE) and a base station (BS or eNB). In the presentdescription, the term “user equipment” or “UE” is used as a generalconcept that includes a terminal in wireless communication. Accordingly,the user equipment (UE) should be construed as a concept that includes amobile station (MS), a user terminal (UT), a subscriber station (SS),and/or a wireless device in a global system for mobile communications(GSM), as well as user equipment used in wideband code division multipleaccess (WCDMA), long term evolution (LTE), and/or high speed packetaccess (HSPA).

A base station or a cell may indicate a station that communicates withthe user equipment. Such a base station may be referred to as differentterms, for example, a Node-B, an evolved Node-B (eNB), a sector, a site,a base transceiver system (BTS), an access point (AP), a relay node(RN), a remote radio head (RRH), a radio unit (RU), and the like.

That is, in the present description, the base station (BS) or the cellmay be construed as an inclusive concept indicating a portion of an areaor a function covered by a base station controller (BSC) in codedivision multiple access (CDMA), a Node-B in WCDMA, an eNB or a sector(a site) in LTE, and the like. Accordingly, a concept of thetransmission/reception point, the base station (BS), and/or the cell mayinclude a variety of coverage areas such as a megacell, a macrocell, amicrocell, a picocell, a femtocell, and the like. Furthermore, suchconcept may include a communication range of the relay node (RN), theremote radio head (RRH), or the radio unit (RU).

In a case of the above-listed various cells, there is a base stationcontrolling each cell. Accordingly, the term “base station” may beconstrued as two meanings. The term “base station” may indicate (i) anapparatus itself providing a megacell, a macrocell, a microcell, apicocell, a femtocell, or a small cell in connection with a wirelessregion, or (ii) the wireless region itself. In the case (i), apparatusesproviding a predetermined wireless region may be controlled by the sameentity. Furthermore, all apparatuses which interact to configure thewireless region through cooperation may be indicated to as “the basestation.” According to a configuration scheme of a wireless region, oneor more of eNB, RRH, an antenna, RU, a low power node (LPN), a point, atransmission/reception point, a transmission point, a reception point,or the like may be embodiments of the base station. In the case (ii),considering from the perspective of user equipment (UE) or the positionof neighboring base stations, the wireless region itself receivingand/or transmitting signals may be referred to as a base station.

Accordingly, a megacell, a macrocell, a microcell, a picocell, afemtocell, a small cell, RRH, an antenna, RU, LPN, a point, eNB, atransmission/reception point, a transmission point, and a receptionpoint may be inclusively referred to as “a base station.”

In the present description, the user equipment and the base station maybe two types of transmission/reception subjects, having an inclusivemeaning, which are used to embody the technology and the technicalconcept disclosed herein, and may not be limited to a specific term orword. Furthermore, the user equipment and the base station may be uplinkor downlink transmission/reception subjects, having an inclusivemeaning, which are used to embody the technology and the technicalconcept disclosed in connection with the present embodiment, and may notbe limited to a specific term or word. Herein, an uplink (UL)transmission/reception is a scheme in which data is transmitted fromuser equipment to the base station. Alternatively, a downlink (DL)transmission/reception is a scheme in which data is transmitted from thebase station to the user equipment.

The wireless communication system may use a variety of multiple accessschemes such as CDMA, time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal frequency division multipleaccess (OFDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA, and/or the like. Suchmultiple access schemes, however, are not limited thereto. At least oneembodiment may be applied to resource allocation in the field ofasynchronous wireless communications evolving to LTE and LTE-advanced(LTE-A) through GSM, WCDMA, and HSP, and in the field of synchronouswireless communications evolving into CDMA, CDMA-2000, and UMB. Thepresent embodiment should not be construed as being limited to orrestricted by a particular wireless communication field, and should beconstrued as including all technical fields to which the spirit of thepresent embodiment can be applied.

In the case of an uplink transmission and a downlink transmission, atleast one of a time division duplex (TDD) and a frequency divisionduplex (FDD) may be used. Herein, the TDD may perform theuplink/downlink transmissions using different times. The FDD may performthe uplink/downlink transmissions using different frequencies.

In a LTE or LTE-A system in conformance with a corresponding standard,an uplink and/or a downlink may be constituted based on one carrier or apair of carriers. In the case of the uplink and/or downlink, controlinformation may be transmitted through such control channels as aphysical downlink control channel (PDCCH), a physical control formatindicator channel (PCFICH), a physical hybrid ARQ indicator channel(PHICH), a physical uplink control channel (PUCCH), and/or so forth.Data may be transmitted through such data channels as a physicaldownlink shared channel (PDSCH), a physical uplink shared channel(PUSCH), and/or the like.

Meanwhile, control information may be transmitted through ‘enhancedPDCCH’ or ‘extended PDCCH’ (EPDCCH). In the present description, theterm “cell” may indicate one of coverage of a signal transmitted from atransmission point or transmission/reception point, a component carrierhaving the coverage, and the transmission/reception point.

A wireless communication system to which at least one embodiment can beapplied may be one of a coordinated multi-point transmission/reception(CoMP) system, a coordinated multi-antenna transmission system, and acoordinated multi-cell communication system. Herein, the CoMP system maytransmit signals through cooperation between a plurality oftransmission/reception points. The wireless communication system such asa CoMP system may include a plurality of multiple transmission/receptionpoints and at least one user equipment (UE).

Multiple transmission/reception points may include eNB and at least oneRRH. Herein, the eNB may be a base station or a macrocell. The RRH maybe wiredly controlled by coupling to the eNB through an optical cable oran optical fiber. Furthermore, the RRH may have either a hightransmission power, or a low transmission power within a macrocellregion.

Hereinafter, a downlink (DL) may represent communication or acommunication path from multiple transmission/reception points (e.g., abase station) to user equipment. An uplink (UL) may representcommunication or a communication path from the user equipment to themultiple transmission/reception points (e.g., a base station). In thedownlink, a transmitter may be a portion of the multipletransmission/reception points, and a receiver may be a portion of theuser equipment. In the uplink, a transmitter may be a portion of theuser equipment, and a receiver may be a portion of the multipletransmission/reception points.

Hereinafter, a situation in which a signal is transmitted or receivedthrough such channels as PUCCH, PUSCH, PDCCH, EPDCCH, and/or PDSCH maybe referred to by the expression “transmit or receive PUCCH, PUSCH,PDCCH, EPDCCH, and/or PDSCH.”

eNB may perform a downlink transmission to at least one user equipment.eNB may transmit PDSCH corresponding to a primary physical channel, forunicast transmission. Furthermore, eNB may transmit PDCCH or EPDCCH inorder to transmit downlink control information, such as schedulinginformation required for receiving PDSCH, and to transmit schedulinggrant information for an uplink data channel (e.g., PUSCH) transmission.Hereinafter, “transmit or receive a signal through a channel” may bereferred to as the expression of “transmit or receive a channel.”

In this case, as described with reference to figures later, a first userequipment (UE1) may transmit an uplink signal to eNB, and a second userequipment (UE2) may transmit an uplink signal to RRH.

In a typical (or existing) 3GPP LTE/LTE-A rel-8/9/10 system, DCI for acertain user equipment such as DL/UL scheduling grant, TPC commands, andso forth may be transmitted through a specific PDCCH (or EPDCCH).Herein, the specific PDCCH may be transmitted through ‘the first one,two, or three OFDM symbols’ (in the case that system bandwidth>10 PRBs)or ‘the first two, three, or four OFDM symbols’ (in the case that systembandwidth≦10 PRBs) in a downlink subframe. Accordingly, in order toreceive ‘DCI for a corresponding user equipment’ transmitted from a basestation (e.g., eNB, RU, RRH, or the like), a certain LTE/LTE-A userequipment may perform a search for whether a PDCCH is transmitted forthe corresponding user equipment, in a PDCCH region which is determinedthrough ‘the first one, two, or three OFDM symbols’ or ‘the first two,three, or four OFDM symbols’ in the downlink (DL) subframe describedabove. Such operation of user equipment may be referred to as “a blinddecoding.” For a blind decoding of the user equipment, a correspondingPDCCH region may be configured with control channel elements (CCEs).Herein, the CCE is a basic unit of PDCCH transmission. In order to formthe CCEs, in an PDCCH region of a certain DL subframe, the remainingresource elements (REs) excluding REs used for PHICH/PCFICH and atransmission of a cell-specific reference signal (CRS) may be dividedinto resource element groups (REGs) which are configured by groupingfour consecutive resource elements (REs) in the frequency axis. Herein,the PHICH and PCFICH correspond to different downlink physical channelswhich are transmitted through a corresponding PDCCH region. The CRScorresponds to a downlink physical signal. As described above, in thecase that REGs corresponding to a unit of resource mapping of CCEs areconfigured, each CCE may be configured with nine interleaved REGs inorder to maximize diversity gain of a PDCCH transmission.

User equipment may perform a blind decoding for whether a PDCCH for theuser equipment is transmitted, in a unit of the CCE. However, to providea sufficient processing time for a PDSCH reception of user equipment andto accomplish a power saving in user equipment, a blind decoding may berequired to be performed for not ‘all CCEs’ but ‘selected CCEs’ of acorresponding PDCCH region. In other words, CCEs to be monitored by userequipment for a blind decoding may be selected per user equipment. Anaggregation of CCEs to be monitored by a given user equipment, i.e.,PDCCH candidates formed by CCEs on which a PDCCH for the given userequipment could be transmitted may be referred to as ‘a search space.’ Atypical (or current) 3GPP LTE/LTE-A system has defined two types ofsearch spaces to be monitored by a given user equipment. That is, thereare a common search space (CSS) and a UE-specific search space (USS).The common search space (CSS) may be monitored by all user equipment ina cell. Such information as PDSCH assignment information for a systeminformation transmission and a random-access response (RAR)transmission, TPC command information, and DL/UL scheduling informationfor a given user equipment may be transmitted through the common searchspace (CSS). Meanwhile, the UE-specific search space (USS) may be aunique search space which is determined for each user equipment. Forexample, DL/UL scheduling information for a corresponding user equipmentmay be transmitted through the UE-specific search space (USS).

In addition, in the case that a PDCCH for a given user equipment istransmitted, an LTE/LTE-A system may support a PDCCH transmission basedon aggregated CCEs. Herein, the PDCCH transmission based on aggregatedCCEs may transmit a PDCCH through a plurality of aggregated CCEs (“notone CCE”) according to a channel state associated with user equipment, asize of DCI to be transmitted to the user equipment, and so forth. Atypical (or current) LTE/LTE-A system may support CCE aggregations. Morespecifically, the typical (or current) LTE/LTE-A system may support aPDCCH transmission based on aggregation level (AL) 1, 2, 4, or 8. Incase of aggregation level (AL) 1, a PDCCH may be transmitted through oneCCE. In case of aggregation levels (ALs) 2, 4, and 8, a PDCCH may betransmitted by binding 2, 4, and 8 CCEs, respectively. Herein, aUE-specific search space (USS) for a given user equipment may beindependently determined per aggregation level (AL). Furthermore, thenumber of PDCCH candidates to be monitored by user equipment, i.e., thenumber of blind decodings to be performed by user equipment may differper aggregation level (AL).

Hereinafter, DCI formats to be blindly decoded per user equipment willbe described in more detail. DCI formats defined in a typical (orcurrent) LTE/LTE-A standard specification may be classified into DCIformat 0/4 (i.e., DCI format 0 and/or DCI format 4), DCI format 1series, DCI format 2 series, and DCI format 3 according to purposes andattributes of information transmitted through a corresponding DCIformat. Herein, The DCI format 0/4 may be used for a transmission of ULscheduling information. The DCI format 1 series and DCI format 2 seriesmay be used for a transmission of DL scheduling grants. The DCI format 3may be used for TPC commands. A given user equipment may perform blinddecodings as many as the number of PDCCH candidates per aggregationlevel (AL) defined above, in a UE-specific search space (USS) for thegiven user equipment. Especially, the given user equipment may performblind decodings only for one or two transmission mode (TM) dependent DCIformats (e.g., downlink DCI format 1/1B/1D/2/2A/2B/2C, and/or uplink DCIformat 4) and fallback DCI format 0/1A among the above-described DCIformats. Herein, with respect to the ‘two’ TM dependent DCI formats, onemay be a PDSCH TM dependent DCI format, and the other may be ‘PUSCH TMdependent DCI format 4’ in PUSCH TM 2. A PDSCH transmission mode (TM)may be configured through high-layer signaling, according to (i)capabilities (e.g., the number of Tx/Rx antennas in each of UE and eNB)of a corresponding user equipment and/or a base station to which theuser equipment belongs, and (ii) channel states between thecorresponding user equipment and the base station. In addition, asdefined in a typical (or current) LTE/LTE-A standard, the number ofPDCCH candidates per aggregation level (AL) may be 6, 6, 2, or 2 foreach aggregation level (AL) 1, 2, 4, or 8. Accordingly, in acorresponding UE-specific search space (USS) for a given user equipment,a blind decoding may be performed 16 times for each of a PDSCH TMdependent DCI format and a fallback DCI format, and therefore beperformed up to a total of 32 times. Alternatively, in the case thatuser equipment is configured as PUSCH transmission mode (TM) 2, a blinddecoding may be further performed 16 times for DCI format 4.Accordingly, in this case, the blind decoding may be performed up to atotal of 48 times.

In the case that user equipment is configured to receive DCI throughEPDCCH, a blind decoding may be defined to be performed in an EPDCCH USS(i.e., a UE-specific search space of the EPDCCH) in place of a legacyPDCCH USS (i.e., a UE-specific search space of a legacy PDCCH), in adownlink (DL) subframe or DwPTS of a special subframe for an EPDCCHmonitoring. Furthermore, in this case, a total of K (“K≧1”) number ofEPDCCH sets may be determined for the user equipment (i.e., userequipment configured to receive DCI through a corresponding EPDCCH) byhigher-layer RRC signaling, along with configuration of the downlink orspecial subframe for the EPDCCH monitoring as described above. Herein,each EPDCCH set may include a group of PRBs (e.g., an N number of PRBs,where N={(1), 2, 4, 8} for a localized EPDCCH set, and N={2, 4, 8, (16)}for a distributed EPDCCH set). A maximum value of the ‘K’ may bedetermined as one of 2, 3, 4, and 6. The number (“N”) of PRBs formingeach EPDCCH set may be independently determined per EPDCCH set.Furthermore, a K number of EPDCCH sets (or set) may be classified into(i) a K_(L) number of localized EPDCCH sets (or set) and (ii) a K_(D)number of distributed EPDCCH sets (or set). Herein, K_(L) and K_(D)satisfy K=K_(L)+K_(D). However, a total number of blind decodings ofuser equipment may be required not to be more than those of a typical(or legacy) system, regardless of values of N, K, K_(L), and K_(D)described above.

In a typical (or legacy) system, the number of CCEs to be monitored peraggregation level (AL) and the number of blind decodings accordingthereto are determined for DCI formats which are configured for areception of a corresponding user equipment. In the case that a K numberof EPDCCH sets (or set) are configured for user equipment, blinddecoding attempts may be required to be distributed per EPDCCH set whilemaintaining a total number of blind decodings being the same as in thetypical (or legacy) system. More specifically, in a typical (or legacy)system, for DCI formats configured for a reception of a correspondinguser equipment, (i) the number of PDCCH candidates to be monitored peraggregation level (AL), (ii) the number of CCEs configuring aUE-specific search space (USS) per aggregation level (AL), and/or (iii)the number of blind decodings according to the above ‘(ii)’ aredetermined according to configuration of PDSCH/PUSCH transmissionmode(s) (TM) as described above. Herein, the above (i) may be consideredfor determination of the above (ii). Accordingly, in the case that a Knumber of EPDCCH sets (or set) are configured for user equipment, thenumber of EPDCCH candidates (i.e., the number of blind decodings to beperformed in a corresponding EPDCCH set) may be required to bedistributed per EPDCCH set while maintaining a total number of blinddecodings being not more than those of the typical (or legacy) system.

In the case that user equipment is configured to receive downlinkcontrol information (DCI) through an EPDCCH corresponding to anewly-adopted downlink control channel, the present embodiment maydefine or provide schemes for performing a blind decoding peraggregation level (AL) in an EPDCCH monitoring set (or EPDCCH monitoringsets) for the user equipment.

In the case that user equipment is configured to receive DCI through anEPDCCH in a system associated with LTE-A release 11 and its follow-uprelease, the present embodiment may provide a blind decoding scheme forthe user equipment. More specifically, the present embodiment mayprovide a scheme of implicitly dividing the number of EPDCCH candidatesper aggregation level (AL), according to the number of EPDCCH setsassigned for a given user equipment and a size of each EPDCCH set (e.g.,the number of PRBs forming a corresponding EPDCCH set).

As described above, in the case that a given user equipment isconfigured to receive DCI through an EPDCCH, a K (“K≧1”) number ofEPDCCH sets (or set) may be configured for the user equipment. In thiscase, each EPDCCH set may include a group of PRBs (e.g., an N number ofPRBs). Furthermore, in case of each EPDCCH set, a type of acorresponding EPDCCH set may be determined as a distributed type or alocalized type. In other words, a K number of EPDCCH sets (or set)configured for an EPDCCH user equipment may be configured with (i) aK_(L) number of localized EPDCCH sets (or set) and (ii) a K_(D) numberof distributed EPDCCH sets (or set). Herein, the EPDCCH user equipmentrepresents user equipment to which EPDCCH is applied. K_(L) and K_(D)satisfy K=K_(L)+K_(D). In the case that an EPDCCH USS (i.e., aUE-specific search space of an EPDCCH) formed for a certain userequipment is configured with a K number of EPDCCH sets (or set), a blinddecoding procedure for reception of downlink control information (DCI)may be performed in a legacy PDCCH CSS and the EPDCCH USS in an ‘EPDCCHmonitoring downlink (DL) subframe’ configured by higher-layer signaling.In this case, a blind decoding UE operation (i.e., a blind decodingoperation of the user equipment) in the legacy PDCCH CSS may beperformed according to operations described in a typical LTE/LTE-Arel-10. A blind decoding UE operation in the EPDCCH USS may be requiredto be defined such that total blind decoding attempts are distributed toa K number of EPDCCH sets (or set) forming a corresponding EPDCCH USSwhile maintaining a total maximum number of blind decoding attempts.Herein, the total maximum number of blind decoding attempts may be “32”(in case of PUSCH TM 1) or “48” (in case of PUSCH TM 2) per componentcarrier (CC).

In addition, user equipment may be configured to monitor an EPDCCH. (i)For normal subframes and normal CP when the number of resources elements(REs) for a possible EPDCCH transmission is less than a threshold value(X_(thresh)) and (ii) for special subframes with special subframeconfiguration 3, 4, or 8 and normal CP when the number of resourceselements (REs) for a possible EPDCCH transmission is less than athreshold value (X_(thresh)) (hereinafter cases (i) and (ii) may bereferred to as “Case 1”), a localized EPDCCH set may be defined tosupport aggregation levels 2, 4, and 8. Otherwise (hereinafter referredto as “Case 2”), the localized EPDCCH set may be defined to supportaggregation levels (ALs) 1, 2, and 4. Furthermore, in Case 1, thelocalized EPDCCH set may be defined to further support aggregation level(AL) 16. In Case 2, the localized EPDCCH set may be defined to furthersupport aggregation level (AL) 8.

Likewise, (i) for normal subframes and normal CP when the number ofresources elements (REs) for a possible EPDCCH transmission is less thana threshold value (X_(thresh)) and (ii) for special subframes withspecial subframe configuration 3, 4, or 8 and normal CP when the numberof resources elements (REs) for a possible EPDCCH transmission is lessthan a threshold value (X_(thresh)) (“Case 1”), a distributed EPDCCH setmay be defined to support aggregation levels 2, 4, 8, and 16. Otherwise(“Case 2”), the distributed EPDCCH set may be defined to supportaggregation levels (ALs) 1, 2, 4, and 8. Furthermore, in Case 1, thedistributed EPDCCH set may be defined to further support aggregationlevel (AL) 32. In Case 2, the distributed EPDCCH set may be defined tofurther support aggregation level (AL) 16. For example, the thresholdvalue (X_(thresh)) used to determine aggregation levels (ALs) supportedin a certain EPDCCH set may be “104”. However, the present embodimentmay be applied regardless of determination of a corresponding thresholdvalue (X_(thresh)).

EPDCCH sets for a certain EPDCCH user equipment may be configured basedon the above-described EPDCCH design criteria. Herein, the EPDCCH userequipment represents user equipment configured to receive DCI through anEPDCCH. In this case, the present embodiment may provide a method ofdetermining the number of EPDCCH candidates per aggregation level (AL)in a corresponding EPDCCH set, and an apparatus therefor. Herein, thenumber of EPDCCH candidates per aggregation level (AL) represents thenumber of EPDCCH candidates to be monitored (i.e., to be blindlydecoded) per aggregation level (AL) by a corresponding user equipment.More specifically, the present embodiment may provide a method and anapparatus for determining the number of EPDCCH candidates to bemonitored per aggregation level (AL) in each EPDCCH set, based on (i)the number of EPDCCH sets formed for a corresponding user equipment,i.e., a K value (or K_(L) and K_(D) values), and (ii) the number of PRBsforming each EPDCCH set, i.e., an N value.

FIG. 1 illustrates a structure for configuration of EPDCCH sets for acertain user equipment in accordance with at least one embodiment. TheEPDCCH set shown in FIG. 1 may be embodied by higher-layer signaling(e.g., RRC signaling).

Referring to FIG. 1, for descriptions of the present embodiment, it maybe assumed that a structure of higher-layer signaling (e.g., RRCsignaling) for configuration of EPDCCH sets for a certain user equipmentis as shown in “110” of FIG. 1. In other words, in such structure,corresponding information region may be hierarchically configured with(i) configuration information (e.g., a K value) associated with thenumber (“K”) of EPDCCH sets formed for a corresponding user equipment,and (ii) configuration information associated with each EPDCCH set(e.g., 1^(st) EPDCCH set configuration information, 2^(nd) EPDCCH setconfiguration information, . . . , K^(th) EPDCCH set configurationinformation). Herein, as shown in “120” of FIG. 1, each EPDCCH setconfiguration information may be configured with information elements(IEs) such as (i) assignment information on a group of PRBs forming acorresponding EPDCCH set (e.g., information on an N₁ number of PRBsforming the corresponding EPDCCH set), and (ii) information on a type ofthe corresponding EPDCCH set. In this case, the number of PRBs formingeach EPDCCH set may be referred to as N₁, N₂, . . . , N_(K), and may bealso referred to as “a size of each EPDCCH set.”

Embodiment 1 corresponding to one of the present embodiments maydistribute the number of EPDCCH candidates per aggregation level (AL),according to ‘the number of EPDCCH sets’ (e.g., “K”).

The number of EPDCCH candidates per aggregation level (AL) to bemonitored in each EPDCCH set by a corresponding user equipment may bedetermined according to a K value corresponding to the number of EPDCCHsets configured for a given user equipment. In other words, in the casethat ‘the total number of EPDCCH candidates per aggregation level (AL)’defined to be monitored by user equipment is referred to as A₁, A₂, . .. , or A_(M), the number of EPDCCH candidates per aggregation level (AL)to be monitored in each EPDCCH set may be determined according toFormula 1 below.

$\begin{matrix}{{{For}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}\mspace{14mu} \# n\mspace{14mu} \left( {{configuration}\mspace{14mu} {of}\mspace{14mu} n^{th}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}} \right)}\left( {{{{where}\mspace{14mu} n} = 1},2,\ldots \mspace{14mu},K} \right){{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 1^{st}{AL}\text{:}\mspace{14mu} \frac{1}{K} \times A_{1}}{{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 2^{nd}{AL}\text{:}\mspace{14mu} \frac{1}{K} \times A_{2}}\vdots {{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} M^{th}{AL}\text{:}\mspace{14mu} \frac{1}{K} \times A_{M}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In other schemes applying Formula 1 above, an information regionindicating aggregation levels (ALs) supported in a corresponding EPDCCHset may be defined in each EPDCCH set configuration information. Thenumber of EPDCCH candidates per aggregation level (AL) may bedistributed based on the newly-defined information region associatedwith AL indication. In an example of defining such information region,AL indicator bits may be defined in each EPDCCH set configurationinformation, according to an M-bit bitmap scheme (i.e., a bitmap schemeusing a bitmap configured with M bits). In this case, each bit in acorresponding bitmap field may be one-to-one mapped to each aggregationlevel (e.g., 1^(st) AL, . . . , or M^(th) AL). Accordingly, such bitmapmay inform a corresponding user equipment of whether each aggregationlevel (AL) is supported in a corresponding EPDCCH set. Morespecifically, in the case that one bitmap bit (i.e., one bit in abitmap) is set to “1”, an aggregation level (AL) corresponding to thebitmap bit may be supported in a corresponding EPDCCH set. Unlike this,in the case that a specific aggregation level (AL) is not supported inthe corresponding EPDCCH set, a bitmap bit corresponding to the specificaggregation level (AL) may be set to “0”. In the case that informationon aggregation levels (ALs) supported in a given EPDCCH set is includedin configuration information of the given EPDCCH set as described above,Formula 1 above may be modified per aggregation level (AL) as describedin Formula 2 below.

$\begin{matrix}{{{For}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}\mspace{14mu} \# n\mspace{14mu} \left( {{configuration}\mspace{14mu} {of}\mspace{14mu} n^{th}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}} \right)}\left( {{{{where}\mspace{14mu} n} = 1},2,\ldots \mspace{14mu},K} \right){{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 1^{st}{AL}\text{:}}\; \left\{ {\begin{matrix}{\frac{1}{K_{1}} \times A_{1}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} 1^{st}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix}{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 2^{nd}{AL}\text{:}\; \left\{ {\begin{matrix}{\frac{1}{K_{2}} \times A_{2}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} 2^{nd}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix}\vdots {Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} M^{th}{AL}\text{:}\left\{ \begin{matrix}{\frac{1}{K_{M}} \times A_{M}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} M^{th}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix} \right.} \right.} \right.} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Formula 2, K_(a) represents the number of EPDCCH sets in which acorresponding bitmap bit of a^(th) AL indicator field is toggled.

An M number of aggregation levels (ALs) defined to support in an EPDCCHset formed for a corresponding user equipment may be arranged inascending order from the lowest AL to the largest AL. In this case,1^(st) AL, . . . , M^(th) AL may represent the arranged aggregationlevels (ALs). In other words, under the above-described EPDDCH designcriteria, in the case that (i) a localized EPDCCH set supportsaggregation levels (ALs) 1, 2, and 4 according to a threshold value(X_(thresh)), and (ii) a distributed EPDCCH set supports aggregationlevels (ALs) 1, 2, 4, and 8, 1^(st) AL, 2^(nd) AL, 3^(rd) AL, and 4^(th)AL may correspond to AL 1, AL 2, AL 4, and AL 8, respectively.Alternatively, in the case that according to a threshold value(X_(thresh)), (i) a localized EPDCCH set supports aggregation levels(ALs) 2, 4, and 8, and (ii) a distributed EPDCCH set supportsaggregation levels (ALs) 2, 4, 8, and 16, 1^(st) AL, 2^(nd) AL, 3^(rd)AL, and 4^(th) AL may correspond to AL 2, AL 4, AL 8, and AL 16,respectively. However, the above-described two cases may correspond to acase that at least one distributed EPDCCH set is configured for a givenuser equipment. If all EPDCCH sets formed for a certain user equipmentare of localized types, aggregation levels (ALs) supported in EPDCCHsets formed for the user equipment may be either “AL 1, AL 2, and AL 4”or “AL 2, AL 4, and AL 8.” Accordingly, 1^(st) AL, 2^(nd) AL, and 3^(rd)AL may correspond to either “AL 1, AL 2, and AL 4” or “AL 2, AL 4, andAL 8,” respectively. The total number of EPDCCH candidates peraggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, and A₄=2,respectively, regardless of satisfaction of a threshold value(X_(thresh)).

In other embodiments, the following three types (e.g., a-1, a-2, a-3) ofvalues may be applied according to combination of types of EPDCCH setsformed for a given user equipment.

a-1) in the case that all EPDCCH sets formed for the given userequipment are of localized type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=4, andA₄=0, respectively.

a-2) in the case that all EPDCCH sets formed for the given userequipment are of distributed type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, andA₄=2, respectively.

a-3) in the case that EPDCCH sets formed for the given user equipmentinclude at least one distributed EPDCCH set and at least one localizedEPDCCH set, the total number of EPDCCH candidates per aggregation level(AL) may be determined as A₁=6, A₂=6, and A₃=2, respectively.Furthermore, in this case, A₄=0 may be applied for the localized EPDCCHset. For the distributed EPDCCH set, A₄=2 and K_(D) (in place of K) maybe applied to the above-described formula for the number of EPDCCHcandidates at 4^(th) AL.

FIG. 2 illustrates the number of EPDCCH candidates in a case ofcombining Embodiment 1 and Formula 1 in accordance with at least oneembodiment. In other words, FIG. 2 illustrates examples to which thecases “a-1,” “a-2,” and “a-3” are applied.

In FIG. 2, “210,” “212,” “214,” “216,” and “218” represent embodimentsin which a localized EPDCCH set supports aggregation levels (ALs) 1, 2,and 4 according to a threshold value (X_(thresh)), and a distributedEPDCCH set supports aggregation levels (ALs) 1, 2, 4, and 8.

“220,” “222,” “224,” “226,” and “228” represent embodiments in which alocalized EPDCCH set supports aggregation levels (ALs) 2, 4, and 8according to a threshold value (X_(thresh)), and a distributed EPDCCHset supports aggregation levels (ALs) 2, 4, 8, and 16.

“210” and “220” represent the number of monitoring candidates in alocalized EPDCCH set, in case of K=1. “212” and “222” represent thenumber of monitoring candidates in localized EPDCCH sets, in case ofK=2. “214” and “224” represent the number of monitoring candidates in adistributed EPDCCH set, in case of K=1. “216” and “226” represent thenumber of monitoring candidates in distributed EPDCCH sets, in case ofK=2. “218” and “228” represent the number of monitoring candidates inone localized EPDCCH set and one distributed EPDCCH set.

The above-described A₁, A₂, A₃, A₄, (A₅) values may merely correspond toexemplary embodiments. A variety of combinations satisfying“A₁+A₂+A₃+A₄=16” or “A₁+A₂+A₃+A₄+A₅=16” may be included in a scope ofthe present invention.

Embodiment 2 corresponding to one of the present embodiments maydistribute the number of EPDCCH candidates per aggregation level (AL),according to a size of an EPDCCH set.

In Embodiment 2, a size of an EPDCCH set may be the number of PRBs.Accordingly, Embodiment 2 may include a distribution scheme based on thenumber of PRBs.

In the case that an EPDCCH set is configured for a certain userequipment, the number of EPDCCH candidates (or the number of blinddecodings according thereto) to be monitored per aggregation level (AL)(i.e., per each of the aggregation levels (ALs) supported in acorresponding EPDCCH set according to an EPDCCH set type) by acorresponding user equipment may be defined. More specifically, thenumber of EPDCCH candidates may be defined such that ‘the total numberof EPDCCH candidates per aggregation level (AL)’ defined to be monitoredby a corresponding user equipment can be distributed to each EPDCCH set,in proportion to ‘a size of each EPDCCH set’ (e.g., N₁, . . . , N_(K)described above) regardless of types of EPDCCH sets. In other words, a Knumber of EPDCCH sets may be allocated for a certain EPDCCH userequipment (i.e., user equipment configured to receive DCI through anEPDCCH). Herein, each of the K number of EPDCCH sets may have a size ofN₁, N₂, . . . , or N_(K). Furthermore, ‘the total number of EPDCCHcandidates per aggregation level (AL)’ defined to be monitored by theuser equipment may be referred to as A₁, A₂, . . . , or A_(M).Accordingly, in this case, ‘the number of EPDCCH candidates peraggregation level (AL)’ to be monitored in each EPDCCH set may bedefined according to Formula 3 below.

$\begin{matrix}{{{For}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}\mspace{14mu} \# n\mspace{14mu} \left( {{configuration}\mspace{14mu} {of}\mspace{14mu} n^{th}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}} \right)}\left( {{{{where}\mspace{14mu} n} = 1},2,\ldots \mspace{14mu},K} \right){{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 1^{st}{AL}\text{:}\mspace{14mu} \frac{N_{1}}{N_{total}} \times A_{1}}{{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 2^{nd}{AL}\text{:}\mspace{14mu} \frac{N_{2}}{N_{total}} \times A_{2}}\vdots {{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} M^{th}{AL}\text{:}\mspace{14mu} \frac{N_{M}}{N_{total}} \times A_{M}}{{{where}\mspace{14mu} N_{total}} = {\sum\limits_{i = 1}^{K}N_{i}}}} & \left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In other schemes applying Formula 3 above, as described in Embodiment 1,an information region indicating an aggregation level (AL) supported ina corresponding EPDCCH set may be defined in each EPDCCH setconfiguration information. The number of EPDCCH candidates peraggregation level (AL) may be distributed based on the newly-definedinformation region associated with AL indication. In an example ofdefining such information region, AL indicator bits may be defined ineach EPDCCH set configuration information, according to an M-bit bitmapscheme (i.e., a bitmap scheme using a bitmap configured with M bits). Inthis case, each bit in corresponding bitmap field may be one-to-onemapped to an aggregation level (e.g., 1^(st) AL, . . . , M^(th) AL).Accordingly, such bitmap may inform a corresponding user equipment ofwhether each aggregation level (AL) is supported in a correspondingEPDCCH set. More specifically, in the case that one bitmap bit (i.e.,one bit in a bitmap) is set to “1”, an aggregation level (AL)corresponding to the bitmap bit may be supported in a correspondingEPDCCH set. Unlike this, in the case that a specific aggregation level(AL) is not supported in the corresponding EPDCCH set, a bitmap bitcorresponding to the specific aggregation level (AL) may be set to “0”.In the case that information on aggregation levels (ALs) supported in agiven EPDCCH set is included in configuration information of the givenEPDCCH set as described above, Formula 3 above may be modified peraggregation level (AL) as described in Formula 4 below.

$\begin{matrix}{{{For}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}\mspace{14mu} \# n\mspace{14mu} \left( {{configuration}\mspace{14mu} {of}\mspace{14mu} n^{th}\mspace{14mu} {EPDCCH}\mspace{14mu} {set}} \right)}\left( {{{{where}\mspace{14mu} n} = 1},2,\ldots \mspace{14mu},K} \right){{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 1^{st}{AL}\text{:}}\; \left\{ {\begin{matrix}{\frac{N_{1}}{N_{{total},1}} \times A_{1}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} 1^{st}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix}{Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} 2^{nd}{AL}\text{:}\; \left\{ {\begin{matrix}{\frac{N_{2}}{N_{{total},2}} \times A_{2}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} 2^{nd}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix}\vdots {Number}\mspace{14mu} {of}\mspace{14mu} {EPDCCH}\mspace{14mu} {candidates}\mspace{14mu} {at}\mspace{14mu} M^{th}{AL}\text{:}\left\{ {{\begin{matrix}{\frac{N_{M}}{N_{{total},M}} \times A_{M}} & {\mspace{11mu} \begin{matrix}{{in}\mspace{14mu} {the}\mspace{14mu} {case}\mspace{14mu} {that}\mspace{14mu} a\mspace{20mu} {bitmap}\mspace{14mu} {bit}\mspace{14mu} {of}\mspace{14mu} M^{th}} \\{{AL}\mspace{14mu} {indicator}\mspace{14mu} {field}\mspace{14mu} {is}\mspace{14mu} {toggled}}\end{matrix}} \\0 & {otherwise}\end{matrix}{where}\mspace{14mu} N_{{total},m}} = {\sum\limits_{i = 1}^{K}{N_{i} \times b_{i,m}}}} \right.} \right.} \right.} & \left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Formula 4, b_(i, m) may represent a bitmap bit value of an indicatorfield corresponding to m^(th) aggregation level (AL) in i^(th) EPDCCHset.

An M number of aggregation levels (ALs) defined to support in an EPDCCHset formed for a corresponding user equipment may be arranged inascending order from the lowest AL to the largest AL. In this case,1^(st) AL, . . . , M^(th) AL may represent the arranged aggregationlevels (ALs). In other words, under the above-described EPDDCH designcriteria, in the case that (i) a localized EPDCCH set supportsaggregation levels (ALs) 1, 2, and 4 according to a threshold value(X_(thresh)), and (ii) a distributed EPDCCH set supports aggregationlevels (ALs) 1, 2, 4, and 8, 1^(st) AL 2^(nd) AL, 3^(rd) AL, and 4^(th)AL may correspond to AL 1, AL 2, AL 4, and AL 8, respectively.Alternatively, in the case that according to a threshold value(X_(thresh)), (i) a localized EPDCCH set supports aggregation levels(ALs) 2, 4, and 8, and (ii) a distributed EPDCCH set supportsaggregation levels (ALs) 2, 4, 8, and 16, 1^(st) AL, 2^(nd) AL, 3^(rd)AL, and 4^(th) AL may correspond to AL 2, AL 4, AL 8, and AL 16,respectively. Accordingly, the total number of EPDCCH candidates peraggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, and A₄=2,respectively, regardless of satisfaction of a threshold value(X_(thresh)).

In other embodiments, the following three types (e.g., b-1, b-2, b-3) ofvalues may be applied according to combination of types of EPDCCH setsformed for a given user equipment.

b-1) in the case that all EPDCCH sets formed for the given userequipment are of localized type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=4, andA₄=0, respectively.

b-2) in the case that all EPDCCH sets formed for the given userequipment are of distributed type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, andA₄=2, respectively.

b-3) in the case that EPDCCH sets formed for the given user equipmentinclude at least one distributed EPDCCH set and at least one localizedEPDCCH set, the total number of EPDCCH candidates per aggregation level(AL) may be determined as A₁=6, A₂=6, and A₃=2, respectively.Furthermore, in this case, A₄=0 may be applied for the localized EPDCCHset. For the distributed EPDCCH set, A₄=2 and K_(D) (in place of K) maybe applied to the above-described formula for the number of EPDCCHcandidates at 4^(th) AL.

In other embodiments, under the above-described EPDDCH design criteria,in the case that (i) a localized EPDCCH set supports aggregation levels(ALs) 1, 2, 4, and 8 according to a threshold value (X_(thresh)), and(ii) a distributed EPDCCH set supports aggregation levels (ALs) 1, 2, 4,8, and 16, 1^(st) AL, 2^(nd) AL, 3^(rd) AL, 4^(th) AL, and 5^(th) AL maycorrespond to AL 1, AL 2, AL 4, AL 8, and AL 16, respectively.Alternatively, in the case that according to a threshold value(X_(thresh)), (i) a localized EPDCCH set supports aggregation levels(ALs) 2, 4, 8, and 16, and (ii) a distributed EPDCCH set supportsaggregation levels (ALs) 2, 4, 8, 16, and 32, 1^(st) AL, 2^(nd) AL,3^(rd) AL, 4^(th) AL, and 5^(th) AL may correspond to AL 2, AL 4, AL 8,AL 16, and AL 32, respectively. Accordingly, the total number of EPDCCHcandidates per aggregation level (AL) may be determined as A₁=6, A₂=6,A₃=2, A₄=1, and A₅=1, respectively, regardless of satisfaction of athreshold value (X_(thresh)).

In other embodiments, the following three types (e.g., c-1, c-2, c-3) ofvalues may be applied according to combination of types of EPDCCH setsformed for a given user equipment.

c-1) in the case that all EPDCCH sets formed for the given userequipment are of localized type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, andA₄=2, respectively.

c-2) in the case that all EPDCCH sets formed for the given userequipment are of distributed type, the total number of EPDCCH candidatesper aggregation level (AL) may be determined as A₁=6, A₂=6, A₃=2, A₄=1,and A₅=1, respectively.

c-3) in the case that EPDCCH sets formed for the given user equipmentinclude at least one distributed EPDCCH set and at least one localizedEPDCCH set, the total number of EPDCCH candidates per aggregation level(AL) may be determined as A₁=6, A₂=6, and A₃=2, respectively.Furthermore, in this case, A₄=1 and A₅=0 may be applied for thelocalized EPDCCH set, A₄=0 and A₅=1 may be applied for the distributedEPDCCH set.

FIG. 3 illustrates the number of EPDCCH candidates in a case ofcombining Embodiment 2 and Formula 3 in accordance with at least oneembodiment. In Embodiment 2, the number of EPDCCH candidates may bedetermined in proportion to a size (e.g., a physical set size) of eachEPDCCH set. Hereinafter, embodiments associated with two or more EPDCCHsets will be described. Furthermore, described will be embodiments whichsupport aggregation levels (ALs) 1, 2, 4, and 8 according to a thresholdvalue (X_(thresh)) in a localized EPDCCH set, and support aggregationlevels (ALs) 1, 2, 4, 8, and 16 in a distributed EPDCCH set.

In FIG. 3, “310” illustrates the number of EPDCCH candidates in the casethat localized EPDCCH sets have the same size. The above-described “c-1”may be applied since two EPCCH sets have the same number of PRBs.Accordingly, for each EPDCCH set (e.g., each of the first and secondEPDCCH set), the number of EPDCCH candidates at AL=1 (corresponding to1^(st) AL) may be “3”. Similarly, for each EPDCCH set, the number ofEPDCCH candidates at AL=2 (corresponding to 2^(nd) AL), AL=4(corresponding to 3^(rd) AL), or AL=8 (corresponding to 4^(th) AL) maybe “3”, “1”, or “1”, respectively.

Meanwhile, “312” illustrates the number of EPDCCH candidates in the casethat localized EPDCCH sets have a different size. As described in “c-1”,A₁=6, A₂=6, A₃=2, and A₄=2 may be applied to “312”. In the case thatFormula 3 is applied, if the number of PRBs of a first localized EPDCCHset is “4” and the number of PRBs of a second localized EPDCCH set is“2”, (i) N_(total) may be “6”,

$({ii})\mspace{14mu} \frac{N_{1}}{N_{total}}$

corresponding to a multiplying factor associated with the firstlocalized EPDDCH set may be ⅔, and

$({iii})\mspace{14mu} \frac{N_{2}}{N_{total}}$

corresponding to a multiplying factor associated with the secondlocalized EPDDCH set may be ⅓. In cases of AL=4 and AL=8, the number ofEPDCCH candidates may be determined as “1”, respectively sincemultiplication results of the multiplying factors are not an integer.

Likewise, in case of distributed EPDCCH sets, the number of EPDCCHcandidates may be determined as shown in “320” and “322”. “320”illustrates a case that distributed EPDCCH sets have the same size.“322” illustrates a case that the number of PRBs of a first distributedEPDCCH set is “4” and the number of PRBs of a distributed EPDCCH set is“2”. “320” and “322” illustrate embodiments to which A₁=6, A₂=6, A₃=2,A₄=1, and A₅=1 determined in “c-2” are applied.

In “320,” in cases of AL=8 and AL=16 for the first distributed EPDCCHset and the second distributed EPDCCH set, it may be that A₄=1 and A₅=1.Accordingly, two distributed EPDCCH sets may be embodied such that thenumber of EPDCCH candidates is selectively determined as “1” as shown in“320”.

In the case that Formula 3 is applied, if the number of PRBs of a firstdistributed EPDCCH set is “4” and the number of PRBs of a seconddistributed EPDCCH set is “2”, (i) N_(total) may be “6”,

$({ii})\mspace{14mu} \frac{N_{1}}{N_{total}}$

corresponding to a multiplying factor associated with the firstdistributed EPDDCH set may be ⅔, and

$({iii})\mspace{14mu} \frac{N_{2}}{N_{total}}$

corresponding to a multiplying factor associated with the seconddistributed EPDDCH set may be ⅓. In cases of AL=4 and AL=8, the numberof EPDCCH candidates may be determined as “1”, respectively sincemultiplication results of the multiplying factors are not an integer.Furthermore, in cases of AL=4, AL=8, and AL=16, the number of EPDCCHcandidates may be selectively determined as “1” as shown in “322”, sinceA₃=2, A₄=1, and A₅=1.

“330” and “332” illustrate the number of EPDCCH candidates in the casethat one localized EPDCCH set and one distributed EPDCCH set areincluded. In this case, if “c-3” is applied, “330” illustrates a casethat two EPDCCH sets have the same size. In “330”, A₁=6, A₂=6, A₃=2,A₄=1, and A₅=0 may be applied for the localized EPDCCH set, and A₁=6,A₂=6, A₃=2, A₄=0, and A₅=1 may be applied for the distributed EPDCCHset. Meanwhile, “332” illustrates a case that two EPDCCH sets have adifferent size. In the case that Formula 3 is applied, if the number ofPRBs of a first EPDCCH set (e.g., a localized EPDCCH set) is “4” and thenumber of PRBs of a second EPDCCH set (e.g., a distributed EPDCCH set)is “2”, (i) N_(total) may be “6”,

$({ii})\mspace{14mu} \frac{N_{1}}{N_{total}}$

corresponding to a multiplying factor associated with the first EPDCCHset (e.g., a localized EPDCCH set) may be ⅔, and

$({iii})\mspace{14mu} \frac{N_{2}}{N_{total}}$

corresponding to a multiplying factor associated with the second EPDCCHset (e.g., a distributed EPDCCH set) may be ⅓. In this case, “c-3” andFormula 3 may be applied. Particularly, as a result of applying “c-3”and Formula 3, the number of EPDCCH candidates having a non-integervalue may be determined as a value calculated by an integer function(i.e., a function of converting a certain non-integer value to aninteger value).

The above-described A₁, A₂, A₃, A₄, (A₅) values may merely correspond toexemplary embodiments. A variety of combinations satisfying“A₁+A₂+A₃+A₄=16” or “A₁+A₂+A₃+A₄+A₅=16” may be included in a scope ofthe present invention.

It may be obvious that other embodiments of applying different schemesper aggregation level (AL) may be included in a scope of the presentinvention. Furthermore, a scheme of obtaining the number of EPDCCHcandidates may be defined to exclude or restrict a case that the numberof EPDCCH candidates per aggregation level (AL) calculated in an EPDCCHset according to the above-described schemes has a non-integer value.Alternatively, in the case that the number of EPDCCH candidates peraggregation level (AL) calculated in an EPDCCH set has a non-integervalue, an integer function (e.g., a ‘ceil’ function, a ‘floor’ function,etc.) may be applied to obtain an integer value which is greater or lessthan a corresponding non-integer value.

Hereinafter, a DCI transmission procedure of a base station and a DCIreception procedure of user equipment will be described in more detail.Herein, the user equipment may be an EPDCCH user equipment configured toreceive DCI through an EPDCCH. Furthermore, in the case that userequipment is configured to receive DCI through an EPDCCH newly-definedin a system associated with 3GPP LTE/LTE-A release 11 and its follow-uprelease, the present embodiment relates to a method of performing ablind decoding in the user equipment, and an apparatus therefor.

FIG. 4 illustrates a procedure of creating an EPDCCH based ondetermination of the number of blind decodings and transmitting thecreated EPDCCH, in a base station in accordance with at least oneembodiment.

At step S410, the base station may calculate the number of blinddecoding candidates (e.g., the number of EPDCCH candidates) according to(i) a resource size of each EPDDCH set (i.e., a resource size associatedwith configuration of each EPDCCH set) and/or (ii) the total number ofEPDCCH sets. In this case, Formula 3 and Formula 4 associated with aresource size of each EPDCCH set may be applied. Alternatively, Formula1 and Formula 2 associated with the total number of EPDCCH sets may beapplied. In other embodiments, such calculation operation for the numberof blind decoding candidates may be performed in advance, and a basestation and user equipment may share the same information (e.g., thenumber of blind decoding candidates). Accordingly, such calculationoperation (e.g., S410) may be selectively performed. At step S420, thebase station may create an EPDCCH by using the number of blind decodingcandidates (e.g., the number of EPDCCH candidates) per aggregation level(AL) in each of one or more EPDCCH sets for the user equipment.Thereafter, at step S430, the base station may transmit the createdEPDCCH to the user equipment.

As described at step S410, the number of blind decoding candidates(e.g., the number of EPDCCH candidates) may be in proportion to (i) aresource size of each EPDDCH set (i.e., a resource size associated withconfiguration of each EPDCCH set) and/or (ii) a reciprocal of the totalnumber of EPDCCH sets. Herein, the resource size may be the number ofphysical resource blocks (PRBs) forming each EPDCCH set. In case of twoor more EPDCCH sets, if Formula 3 is applied, the number of blinddecoding candidates (e.g., the number of EPDCCH candidates) peraggregation level (AL) in each EPDCCH set may be determined according toa ratio created by dividing the number of PRBs forming one EPDCCH set bythe number of PRBs forming total EPDCCH sets. Furthermore, in this case,if the ratio is not an integer, the number of blind decoding candidates(e.g., the number of EPDCCH candidates) may be determined by applying aninteger function (i.e., a function of converting a certain non-integervalue to an integer value) or a predetermined integer.

Meanwhile, the base station may inform the user equipment of the numberof blind decoding candidates (e.g., the number of EPDCCH candidates)determined at step S410. More specifically, the base station maytransmit information indicating the number of blind decoding candidates(e.g., the number of EPDCCH candidates) per aggregation level (AL) ineach EPDCCH set, to the user equipment.

FIG. 5 illustrates a procedure of adjusting a blind decoding procedurein an EPDCCH region using the number of blind decodings, in userequipment in accordance with at least one embodiment.

At step S510, the user equipment may receive a downlink signal from abase station. At step S520, the user equipment may perform a blinddecoding in an EPDCCH region of the received downlink signal, byapplying the number of blind decoding candidates (e.g., the number ofEPDCCH candidates) per aggregation level (AL) in each of one or moreEPDCCH sets. Herein, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be in proportion to (i) a resource sizeof each EPDDCH set (i.e., a resource size associated with configurationof each EPDCCH set) and/or (ii) a reciprocal of the total number ofEPDCCH sets. Herein, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be calculated according to (i) Formula3 and Formula 4 associated with a resource size of each EPDCCH set, or(ii) Formula 1 and Formula 2 associated with the total number of EPDCCHsets. In other embodiments, such calculation operation for the number ofblind decoding candidates may be performed in advance, and a basestation and user equipment may share the same information (e.g., thenumber of blind decoding candidates).

As described above, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be in proportion to (i) a resource sizeof each EPDDCH set (i.e., a resource size associated with configurationof each EPDCCH set) and/or (ii) a reciprocal of the total number ofEPDCCH sets. Herein, the resource size may be the number of physicalresource blocks (PRBs) forming each EPDCCH set. In case of two or moreEPDCCH sets, if Formula 3 is applied, the number of blind decodingcandidates (e.g., the number of EPDCCH candidates) per aggregation level(AL) in each EPDCCH set may be determined according to a ratio createdby dividing the number of PRBs forming one EPDCCH set by the number ofPRBs forming total EPDCCH sets. Furthermore, in this case, if the ratiois not an integer, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be determined by applying an integerfunction (i.e., a function of converting a certain non-integer value toan integer value) or a predetermined integer.

Meanwhile, in order to share the number of blind decoding candidatesbetween a base station and user equipment, the user equipment mayreceive information indicating the number of blind decoding candidates(e.g., the number of EPDCCH candidates) per aggregation level (AL) ineach EPDCCH set, from the base station.

In FIG. 4 and FIG. 5, a base station and user equipment may have thenumber of blind decoding candidates (e.g., the number of EPDCCHcandidates) in form of table, in advance. Alternatively, a base stationmay inform user equipment of the number of blind decoding candidates(e.g., the number of EPDCCH candidates), through indication information.In other embodiments, user equipment may calculate the number of blinddecoding candidates (e.g., the number of EPDCCH candidates) peraggregation level (AL) in each EPDCCH set, according to the same schemeas in a base station. A scheme in which a base station and userequipment share information on the number of blind decoding candidates(e.g., the number of EPDCCH candidates) may be variously embodied, andthe present embodiments are not limited to a specific sharing scheme.

FIG. 6 is a diagram illustrating a structure of a base station inaccordance with some embodiments.

Referring to FIG. 6, base station 600 according to at least oneembodiment may include control processor 610, transmitter 620, andreceiver 630.

Control processor 610 may control operations (i.e., operations of basestation 600) which are required for performing the above-describedpresent embodiments. More specifically, control processor 610 maycontrol operations (i.e., operations of base station 600) associatedwith a downlink control information (DCI) reception of user equipment.Herein, the user equipment is configured to receive downlink controlinformation (DCI) through an EPDCCH.

Transmitter 620 and receiver 630 may respectively transmit and receivesignals, messages, and/or data required for performing theabove-described present embodiments, in connection with the userequipment. Base station 600 shown in FIG. 6 may perform a base stationoperation described in FIG. 4.

More specifically, control processor 610 may create an EPDCCH using thenumber of blind decoding candidates (e.g., the number of EPDCCHcandidates) per aggregation level (AL) in each of one or more EPDCCHsets for the user equipment. Transmitter 620 may transmit the createdEPDCCH to the user equipment. As described above, the number of blinddecoding candidates (e.g., the number of EPDCCH candidates) may be inproportion to (i) a resource size of each EPDDCH set (i.e., a resourcesize associated with configuration of each EPDCCH set) and/or (ii) areciprocal of the total number of EPDCCH sets.

The number of blind decoding candidates (e.g., the number of EPDCCHcandidates) may be in proportion to (i) a resource size of each EPDDCHset (i.e., a resource size associated with configuration of each EPDCCHset) and/or (ii) a reciprocal of the total number of EPDCCH sets.Herein, the resource size may be the number of physical resource blocks(PRBs) forming each EPDCCH set. In case of two or more EPDCCH sets, ifFormula 3 is applied, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) per aggregation level (AL) in each EPDCCHset may be determined according to a ratio created by dividing thenumber of PRBs forming one EPDCCH set by the number of PRBs formingtotal EPDCCH sets. Furthermore, in this case, if the ratio is not aninteger, the number of blind decoding candidates (e.g., the number ofEPDCCH candidates) may be determined by applying an integer function(i.e., a function of converting a certain non-integer value to aninteger value) or a predetermined integer. Furthermore, transmitter 620may transmit information indicating the number of blind decodingcandidates (e.g., the number of EPDCCH candidates) per aggregation level(AL) in each EPDCCH set, to the user equipment.

FIG. 7 is a diagram illustrating a structure of user equipment inaccordance with some embodiments.

Referring to FIG. 7, user equipment 700 according to at least oneembodiment may include control processor 710, transmitter 720, andreceiver 730.

Receiver 730 may receive downlink control information, data, and/ormessages through a corresponding channel from a base station (e.g., basestation 600).

Control processor 710 may control operations (i.e., operations of useequipment 700) which are required for performing the above-describedpresent embodiments. More specifically, control processor 710 maycontrol operations (i.e., operations of user equipment 700) associatedwith a downlink control information (DCI) reception of user equipment700. Herein, user equipment 700 is configured to receive downlinkcontrol information (DCI) through an EPDCCH.

Transmitter 720 may transmit control information, data, and/or messagesthrough a corresponding channel, to the base station. User equipment 700shown in FIG. 7 may perform a user equipment operation described in FIG.5.

Receiver 730 may receive a downlink signal from a base station. Controlprocessor 710 may perform a blind decoding in an EPDCCH region of thereceived downlink signal, by applying the number of blind decodingcandidates (e.g., the number of EPDCCH candidates) per aggregation level(AL) in each of one or more EPDCCH sets. Herein, the number of blinddecoding candidates (e.g., the number of EPDCCH candidates) may be inproportion to (i) a resource size of each EPDDCH set (i.e., a resourcesize associated with configuration of each EPDCCH set) and/or (ii) areciprocal of the total number of EPDCCH sets.

As described above, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be in proportion to (i) a resource sizeof each EPDDCH set (i.e., a resource size associated with configurationof each EPDCCH set) and/or (ii) a reciprocal of the total number ofEPDCCH sets. Herein, the resource size may be the number of physicalresource blocks (PRBs) forming each EPDCCH set. In case of two or moreEPDCCH sets, if Formula 3 is applied, the number of blind decodingcandidates (e.g., the number of EPDCCH candidates) per aggregation level(AL) in each EPDCCH set may be determined according to a ratio createdby dividing the number of PRBs forming one EPDCCH set by the number ofPRBs forming total EPDCCH sets. Furthermore, in this case, if the ratiois not an integer, the number of blind decoding candidates (e.g., thenumber of EPDCCH candidates) may be determined by applying an integerfunction (i.e., a function of converting a certain non-integer value toan integer value) or a predetermined integer. Receiver 730 may receiveinformation indicating the number of blind decoding candidates (e.g.,the number of EPDCCH candidates) per aggregation level (AL) in eachEPDCCH set, from the base station.

As described above, since the technical idea of the present invention isdescribed by exemplary embodiments, various forms of substitutions,modifications and alterations may be made by those skilled in the artfrom the above description without departing from essential features ofthe present invention. Therefore, the embodiments disclosed in thepresent invention are intended to illustrate the technical idea of thepresent invention, and the scope of the present invention is not limitedby the embodiment. The scope of the present invention shall be construedon the basis of the accompanying claims in such a manner that all of thetechnical ideas included within the scope equivalent to the claimsbelong to the present invention.

1-16. (canceled)
 17. A method of adjusting a blind decoding of adownlink control channel in a base station, the method comprising:creating an enhanced physical downlink control channel (EPDCCH) usingthe number of EPDCCH candidates per aggregation level (AL) in each ofone or more EPDCCH sets for user equipment; and transmitting the createdEPDCCH to the user equipment, wherein in a case of two EPDCCH sets havethe same resource size, the number of EPDCCH candidates per aggregationlevel (AL) in each EPDCCH set is determined same number.
 18. The methodof claim 17, wherein the number of EPDCCH candidates associated with apart or all of corresponding aggregation levels (ALs) in the one EPDCCHset or in a part or all of the EPDCCH sets is in proportion to at leastone of (i) the resource size associated with configuration of eachEPDCCH set and (ii) a reciprocal of the total number of EPDCCH sets. 19.The method of claim 17, wherein the resource size is the number ofphysical resource blocks (PRBs) forming each EPDCCH set.
 20. A method ofadjusting a blind decoding of a downlink control channel in userequipment, the method comprising: receiving a downlink signal from abase station; and performing a blind decoding procedure in an EPDCCHregion of the received downlink signal, by applying the number of EPDCCHcandidates per aggregation level (AL) in each of one or more EPDCCHsets, wherein in a case of two EPDCCH sets have the same resource size,the number of EPDCCH candidates per aggregation level (AL) in eachEPDCCH set is determined same number.
 21. The method of claim 20,wherein the number of EPDCCH candidates associated with a part or all ofcorresponding aggregation levels (ALs) in the one EPDCCH set or in apart or all of the EPDCCH sets is in proportion to at least one of (i)the resource size associated with configuration of each EPDCCH set and(ii) a reciprocal of the total number of EPDCCH sets.
 22. The method ofclaim 20, wherein the resource size is the number of physical resourceblocks (PRBs) forming each EPDCCH set.
 23. User equipment for adjustinga blind decoding of a downlink control channel, the user equipmentcomprising: a receiver configured to receive a downlink signal from abase station; and a control processor configured to perform a blinddecoding in an EPDCCH region of the received downlink signal, byapplying the number of EPDCCH candidates per aggregation level (AL) ineach of one or more EPDCCH sets, wherein in a case of two EPDCCH setshave the same resource size, the number of EPDCCH candidates peraggregation level (AL) in each EPDCCH set is determined same number. 24.The user equipment of claim 23, wherein the number of EPDCCH candidatesassociated with a part or all of corresponding aggregation levels (ALs)in the one EPDCCH set or in a part or all of the EPDCCH sets is inproportion to at least one of (i) the resource size associated withconfiguration of each EPDCCH set and (ii) a reciprocal of the totalnumber of EPDCCH sets.
 25. The user equipment of claim 23, wherein theresource size is the number of physical resource blocks (PRBs) formingeach EPDCCH set.